4 
' Theory of Compound Sounds. 657 
are sounded separately ; and I appeal to common 
experience to determine, if they are not equally 
distinct when heard in concert. Taking it for 
granted that the answer will be in the affirmative, 
I pronounce the aggregate to be a mixture of 
sounds in one case. Secondly, if a violin sound 
in front of the hearer, and a flute be heard at 
the same time in an oblique situation, the person 
thus circumstanced is able to determine the re- 
lative positions of the two instruments, which 
shews the aggregate to have two cotemporary 
directions, It is therefore a mixture of sounds, 
not a single sound, Thirdly, I have found by 
making the experiment, that any number of mu- 
sical strings may be made to vibrate by a com- 
pound sound acting upon them, provided this 
compound be occasioned by an equal number of 
strings with the former, having one in the latter 
Set in unison with each one in the preceding set: 
This is an experimental proof that there are as 
Many sets of pulses in an aggregate of sounds 
as that aggregate contains elements, because no 
string whatever is in unison with a concord or 
discord. Lastly, if it were possible for sounds 
to coalesce, men would never hear any thing 
more than one noise at one time: The general 
hum would have varied perpetually from the ex- 
tinction of existing sounds, and the! intrusion of 
fresh ones; but the human mind»would have 
